A conventional electric braking device for a vehicle includes an “electric motor generating power”, a “pressing member (brake piston) pressing a friction member (pad) against a rotating member (brake disk) integrally rotating together with a wheel of a vehicle”, a “power transmitting mechanism transmitting the power generated by the electric motor to the pressing member to generate pressing force of the pressing member with respect to the friction member”, and a “control means controlling a power supply amount for the electric motor such that the pressing force depending on an operation of a brake operation member (brake pedal) of the vehicle by a driver” (for example, see Patent Literature 1).
In the device described in the above literature, a hysteresis characteristics in a relationship between the “power supply amount for the electric motor” and the “pressing force of the pressing member” is acquired in advance. In the literature, when braking force having an almost constant magnitude continues for a predetermined time or longer, the power supply amount is reduced in consideration of the hysteresis characteristics within a range in which the braking force can be kept. In this manner, a current consumption in the device can be reduced.
The hysteresis characteristics may successively vary because aging, a change in temperature, and the like of a sliding part in a power transmitting mechanism causes a frictional coefficient of the sliding part to vary. However, the literature does not describe a variation in hysteresis characteristic at all.
When a range (range of a power supply amount at which pressing force can be kept) of actual hysteresis characteristics is larger than a range of the hysteresis characteristics acquired in advance, a power supply amount is reduced but a margin to be able to further reduce the power supply amount within the range in which the braking force can be kept is left. In this case, there is a margin to be able to further reduce a current consumption of the device. On the other hand, when the range of the actual hysteresis characteristics is smaller than the range of the hysteresis characteristics acquired in advance, the power supply amount might be reduced over the range in which the braking force can be kept. In this case, a situation in which the braking force cannot be kept (the braking force reduces) may occur.